Doug G summed it up exactly. As we both pointed out, there is no mileage interval and unless a customer has a shift related complaint, no one will just do a flush. There are times too when not every tech will be equally savvy enough to ask others or check for possible written TSBs. Usually only a more experienced tech would do that so there's times when if you know about a specific TSB, it's then not a bad idea to remind your service adviser.